This paper analyzes the effects of complex geometries on three-dimensional (3D) slope stability using an elastoplastic finite difference method (FDM) with a strength reduction technique. A series of special 3D slopes with various geometric configurations, including curving slope surface, turning corners, turning arcs, and turning forms, is presented in terms of factor of safety, shear slip surface, and deformed mesh. More than 180 cases with various geometries for different slope gradient (90°, 45°, and 26.57°) under different boundary conditions (smooth–smooth, rough–smooth, and rough–rough) are calculated and discussed in detail. Many interesting results are obtained and some of them appear to be surprising. These results can be used directly to offer suggestions for landslide hazard preparedness or safe and economical design of infrastructures, e.g., excavations, embankments, and so on.